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Cold sores: Overview

What is a cold sore?

A cold sore is a small blister or group of blisters that usually develop on the lip or around the mouth. Cold sores are caused by the herpes simplex virus (HSV).

Cold sores are also known as fever blisters or herpes simplex labialis

If you get cold sores, you’re not alone. More than half of Americans ages 14 to 49 carry the virus that causes cold sores. The virus stays in the body after the cold sores clear. If the virus reactivates, or wakes up, you may get cold sores again.

Cold sores are generally not serious. In healthy people, cold sores tend to clear within two weeks.

Cold sore on and above the lip

Cold sores are so contagious that many people catch the virus that causes them by the time they’re 5 years old.

Cold sore on and above the lip

If you have a cold sore, you can spread the virus to others who don’t have the virus. Even when you treat cold sores, you can still spread the virus to others. You are contagious until all the sores have scabbed over.

By taking the following precautions until all of the sores have scabs, you can avoid infecting others:

  • Don't kiss people, especially children

  • Avoid other intimate contact

  • Avoid close contact with anyone who has a weakened immune system, including newborn babies

  • Don’t share personal items like lip balm, towels, or razors

  • Don’t share beverages or food

  • Try not to touch your cold sores

  • If you touch a cold sore or apply medicine to it, wash your hands immediately afterward

  • Wash your hands frequently throughout the day

These precautions are especially important if you are around a child who has eczema or someone who has a weakened immune system. If that person catches the virus, it can be very serious.

Related AAD resource

Getty Images

American Academy of Dermatology. “Dermatologists share tips for treating cold sores.” News release issued April 15, 2015.

Fatahzadeh M and Schwartz RA. “Human herpes simplex virus infections: Epidemiology, pathogenesis, symptomatology, diagnosis, and management.” J Am Acad Dermatol. 2007;57(5):737-63.